With advances in drilling technology, it is currently possible to drill horizontal wellbores deep into hydrocarbon producing reservoirs. There are many advantages to a horizontal well completion including extending contact with a producing formation thereby facilitating drainage and production of the reservoir.
Although horizontal wellbores allow more contact with the producing formation, one encounters some difficulties in well completions associated with horizontal wellbores not commonly dealt with in vertical wells. One area of concern in well completions is the inability to effectively cement voids along the horizontal section during a cementing operation. Effective cementing of the tubing to the wellbore is routinely accomplished in vertical wellbores. However, in horizontal wellbores and severely inclined wellbores, i.e. those having an angle of deviation greater than about 45.degree., cementing is much more difficult. Therefore, the efficiency of zone isolation diminishes considerably.
In oil and gas well completions it is imperative to effectively isolate the oil or gas bearing formation from other zones in the wellbore. This is most frequently accomplished by cementing the production casing in place and then perforating the wellbore in the production horizon to allow hydrocarbon flow into the wellbore. With effective cementing, flow up the outside of the production casing is eliminated and the oil and/or gas producing zone is effectively isolated.
Often a failure of the cementing operation occurs in horizontal wellbores because the density of the cement does not allow sufficient displacement of drilling mud and other residue from the tubing/wellbore annulus, thereby resulting in channeling of cement and improper tubing or pipe/formation bonding. Failure also occurs because the annular space between the wellbore and casing is not adequately cleaned of debris prior to initiating the cementing operation.
Therefore, what is needed is a method for improving the effectiveness of the cementing operation in deviated or horizontal wellbores which allows complete removal of debris from the annulus and the removal of void spaces in the horizontal section due to incomplete displacement of wellbore materials and the effects of gravity on high density cement.